Pintos Operating System Project

🚀 Project Overview

This project is an implementation of an educational operating system, Pintos, originally developed for Stanford's CS 140 and later adapted by UC Berkeley for CS 162. The project involves enhancing the Pintos kernel by implementing functionalities such as multithreading, user program execution, system calls, and an enhanced file system.

🛠 Features Implemented

The project was divided into three major phases, each focusing on different aspects of OS development:

1️⃣ User Programs & System Calls

• Implemented system calls including halt, exit, exec, wait, create, remove, open, close, read, write, file-size, tell, and seek.
• Implemented argument passing to support command-line arguments for user programs.
• Enhanced thread structure to support process execution.
• Implemented process control mechanisms like wait and exec.
• Added proper exit handling to track and manage processes.
• Implemented file descriptors to manage opened files.

2️⃣ Threads & Scheduling

• Implemented a priority scheduler for better CPU utilization.
• Added priority donation to handle priority inversion.
• Modified semaphores and condition variables to support priority donation.
• Improved synchronization mechanisms using locks, semaphores, and condition variables.
• Implemented Multi-Level Feedback Queue (MLFQ) scheduler.
• Added Shortest Remaining Time First (SRTF) scheduling algorithm.
• Optimized sleeping thread wakeup mechanism.

3️⃣ File System

• Implemented persistent file storage.
• Extended the file system to support directories and file descriptors.
• Implemented directory support, including mkdir, chdir, and readdir system calls.
• Improved disk buffer caching for performance.
• Implemented inode locking mechanisms to ensure file system consistency.
• Improved file system synchronization with proper locking strategies.
• Implemented file extension support and indirect/doubly indirect block handling.
• Implemented write protection for executable files.

📂 Project Structure

📦 pintos
├── src
│   ├── devices      # Device drivers for timers, disks, and input handling
│   ├── examples     # Example programs for testing and demonstration
│   ├── filesys      # File system implementation with directories, inodes, and caching
│   ├── lib          # Library functions used by various components
│   ├── memory       # Memory management and paging support
│   ├── misc         # Miscellaneous utilities and helper functions
│   ├── tests        # Test cases for various components
│   ├── threads      # Core threading and synchronization primitives
│   ├── userprog     # Process execution, system calls, and user program handling
│   ├── utils        # Utility scripts and helper functions
│   └── vm           # Virtual memory (not implemented in this version)
└── README.md

⚙️ Installation & Setup

To set up and run Pintos on your local machine:

Prerequisites

• Linux (Ubuntu recommended) or macOS
• GCC, GDB, Make (for compiling and debugging)

▶️ Running Pintos

cd pintos/src
make
make check  # Runs the test suite
pintos -- run <test-program>

🎯 Challenges & Learning Outcomes

• Kernel Synchronization: Designed thread-safe mechanisms using locks and semaphores.
• Process Management: Learned about memory layout, process loading, and execution.
• File Systems: Implemented persistent storage and file caching optimizations.
• Low-Level Debugging: Gained experience with GDB, backtraces, and kernel debugging tools.

📜 License

This project is for educational purposes. Feel free to fork, modify, and use it for learning!

🔗 References

• Pintos Documentation
• CS 162 Course Materials

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Made with ❤️ and a LOT of debugging 🛠️